Peroxide bleaching agents for the use in laundring have been known for many years. Such agents are effective in removing stains, such as tea, fruit, and wine stains, from clothing at or near boiling temperatures. The efficacy of peroxide bleaching agents drop off sharply at temperatures below 60.degree. C.
Previous patent applications dealt with environmentally acceptable manganese ions and complexes. U.S. Pat. No. 4,728,455 discusses the use of Mn(III)-gluconate as peroxide bleach catalyst with high hydrolytic and oxidative stability; relatively high ratios of ligand (gluconate) to Mn are, however, needed to obtain the desired catalytic system. Moreover, the performance of these Mn-based catalysts is inadequate when used for bleaching in the low-temperature region of about 20.degree.-40.degree. C., and they are restricted in their efficacy to remove a wide range of stains.
In several patent documents, for instance EP-A-458,379, novel triazacyclononane-based manganese complexes are disclosed, which display a high catalytic oxidation activity at low temperatures, which is particularly suitable for bleaching purposes. A major improvement of the bleaching activity could be obtained by the fact that these compounds are stable under washing conditions, e.g. high alkalinity and oxidizing environment (as a result of the presence of hydrogen peroxide or peroxy acids).
In addition to the above-mentioned stain removal, dye transfer is a well-known problem in the art and has been addressed in various ways. For instance, an improved dye transfer inhibition has been obtained by using Fe-porphyrin and Fe-phtalocyanine complexes (see EP-A-537,381, EP-A-553,607, EP-A-538,228).
It is well known that the stability of Fe-co-ordination complexes in alkaline aqueous media in the presence of peroxide compounds is very poor; in EP-A-537,381 and EP-A-553,607, methods are disclosed for improvement in this respect.
This poor stability of Fe-co-ordination species has resulted in the necessity of very low concentrations of peroxide and, additionally, the use of polymers (see EP-A-538,228). These measures, however, only reduce the negative effects of the above-indicated poor stability to some extent and do not provide a complete solution for this problem.
We have now surprisingly found catalytically highly active iron compounds which can activate hydrogen peroxide or peroxy acids,thereby providing both favourable stain removal, remarkable dye transfer inhibition properties, and, alternatively, oxidation of organic substrates such as olefins, alcohols and unactivated hydrocarbons.
In addition, a considerably improved stability of these compounds in alkaline aqueous environment has been obtained, in particular at the peroxy compound concentrations generally present in the wash liquor during the fabric washing cycle.